Digital signatures (digital fingerprints) can find application in many contexts. Merely one example of a field of application is audience measurement/analysis, as explained below.
Audience measurement/analysis systems, for measuring/analysing TV or radio audiences for instance, commonly make use of so-called meters installed in a panel of households, or on a panel of persons, generally chosen such that the household occupants or persons are demographically representative of the potential audience population as a whole.
The meters are devices which monitor the channels, stations or programs selected for viewing or listening on a TV or radio in the household, or by the person, and typically record information concerning the selected channels, stations or programs for sending, for example by telephone line or other means of communication, to a “central” or “reference” office at which viewing/listening information from households in the panel is collected for analysis.
In the central or reference office all or many channels, stations or programs available for viewing or listening may be monitored and information concerning those channels, stations or programs stored as reference information. Reference information may also be obtained from other sources. For example information concerning programs broadcast on a particular channel or station over a period of time may be obtained directly from the broadcasting company. The information from households/persons may then be analysed to reveal channels, stations or programs selected for viewing in the households or by persons, by comparison or matching of information from the households/persons with the reference information.
Various techniques for household or personal monitoring of channels, stations or programs have been put to use. Similar techniques may in general be used in the central or reference office for monitoring all or many channels, stations or programs available for viewing or listening.
One technique used at least in households is to directly monitor tuning circuits in a TV or radio set, to gain information about the channel (frequency) to which the set is tuned. Another technique is to monitor special identification codes embedded in program signals, for example as broadcast or delivered by a service provider. The codes are embedded “at source” in the program signal by the service provider, for example in an audio signal component, or in an video signal component if video is involved. Such embedded codes typically identify the broadcasting station, and may also containing information identifying the program carried by the station at any given time. A third technique is to derive, from a program selected for viewing or listening, a signature (i.e. fingerprint) characteristic of the program. The signature may be derived from audio or video. Such a signature is not embedded in the program signal at source, but is derived or generated from the program signal at the point of viewing or listening in a household or by a person.
Each of these methods has been perceived to have disadvantages.
Directly monitoring tuning circuits typically requires physical entry into and modification of a TV or radio set concerned, and is therefore undesirably invasive.
Monitoring embedded identification codes, even if physical entry into and modification of a TV or radio set concerned is not always needed, effectively requires such codes to be embedded at source and to be reliably detectable in all, or substantially all, programs. If this is not the case, the information obtained is at best incomplete, likely to the extent that it is of little or no utility.
The use of signatures/fingerprints has been considered to be demanding in terms of cost and the hardware needed, and susceptible in practice to program identification problems due to inconsistencies between signatures/fingerprints generated, on the basis of the same original program content, under the different conditions which may apply at different locations and different times. The different conditions may arise as a result of different program reception conditions or equipment capabilities at different times or locations, for example in a household or at a person on the one hand and at a central or reference office on the other hand.
Not only in this context, there are many applications in which it is desirable to identify a signature/fingerprint, or a sequence of signatures/fingerprints, for example representing a section of audio, from within reference information or a reference database, e.g. of audio, available at a central or reference office. To achieve this it is necessary to generate robust digital fingerprints, e.g. from audio samples, such that if the same original sample, e.g. and audio sample, after having experienced various distortions were to be used to also generate digital fingerprints, an exact or relatively similar fingerprint would be generated, thereby allowing identification, for example by a searching or matching algorithm, of the original audio sample.
Thus, the fingerprints should allow searching from one set of fingerprints (e.g. derived in a household or at a person) within another set (e.g. available at a central or reference office), with the goal of determining if fingerprints from one set match any fingerprints from the other set thereby determining a match.
As mentioned above, one such field in which such identification is desirable is the media audience measurement market. A user or audience member is exposed to audio, for example, produced from television, radio, internet, or similar broadcast.
Another field is in the arena of digital copyright management (DRM—Digital Rights Management). For example, it is desirable to be able to identify if media—e.g. audio media—posted on the internet is in fact copyright material.
Yet another field of the invention is in royalty distribution. Frequently, media broadcasts utilize copyright material. The artist or publisher of this material allows their art to be broadcast usually in return for compensation. Typically, there are royalty distribution organizations that collect funds from the broadcasters or users of the material and distribute the funds to the artists and/or publishers of the material depending on the usage. Digital signatures/fingerprints can be used to identify which copyright material is being broadcast such that the artist or publisher of the material will be duly compensated.